How to Spy on Your Sister While on a Triple Date
by TheFluffyPrince
Summary: There was no way that Rin was just going to let Seijuurou go out on a date with his sister without his supervision.


**A/N: So, I've finally decided to write Captain/Kou, because I find them really cute and they need more stories out there (I still haven't learned the Captain's name, so I just call him Captain in my notes). I'll hopefully know his name by the end of this story though.**

**The hardest part of writing Kou is trying to figure out which name to go with. So I did both. ;A:**

**Pairing: SeiKou/SeiGou (I, personally, call her Kou) (with minor ReiGisa, MakoHaru, RinTori)**

**Warning: Fluff, overprotective brother**

**Disclaimer: I don't own Free!/Swimming anime**

* * *

"I don't think you should go out on this date, Gou," Rin said from his spot on the couch, a frown present on his face.

A sigh left Kou's mouth and she glared at her brother from across the room. Her hands rested on her hips for a moment, ceasing their worrying movements. "Rin, you've said this three times and my answer still hasn't changed. I am going on a date with Seijuurou. Yes, I am completely sure about this. And no, I don't want you to come along! So let it go already!" Kou huffed and turned back around towards the mirror, fixing her hair even though it was already okay.

Rin just growled underneath his breath, his eyes narrowed and his arms crossed. He didn't like this one bit. Sure, it was his swim captain that was going out with his sister, and he did trust Seijuurou (he saw the guy everyday and knew him considerably well, after all). It was just that...Kou was his little sister. In his eyes, no guy was good enough to date his sister. Even the guy who helped him with his swimming regimen.

A sudden knock pierced through the tense atmosphere, shattering it in an instant. Kou and Rin turned their heads towards the door, their expressions changing in an instant. A bright smile came to Kou's face while a scowl came to Rin's. He watched with irritated eyes as his younger sister practically skipped towards the door, opening it to reveal Seijuurou behind it.

The swim captain jumped a bit, a shy smile on his face. A faint blush came to his cheeks as he saw Kou and he he stuck out his hand, revealing a single rose. A gasp left the redhead's mouth before she smiled even brighter, taking the flower from Seijuurou's hand and sniffing it.

"H-Hi, Gou-chan. I hope y-you like the f-flower," Seijuurou stammered softly, blushing a little bit more.

Looking at the swim captain from over the flower, Kou giggled softly and nodded her head. "I...I do. Thank you, Seijuurou."

The swim captain nodded his head quickly, coughed awkwardly before glancing down at his watch. It wouldn't be a while until they had to be to the restaurant, so there was no need to hurry. As he did that though, he could feel another pair of eyes practically boring into him from inside of the home and it was really making him uncomfortable. He knew that it was Rin that was glaring at him, but he didn't really want to lift his head up and lock eyes with him. It was part of the reason why he was kind of hesitant on picking Gou up from her house. However, like the gentleman that he was, he refused to make his girlfriend drive to their date. He insisted that he would pick her up.

Now, he was kind of starting to regret that.

Noticing Seijuurou getting even more nervous (if that was possible), Kou looked over her shoulder and saw her brother practically snarling at his swim captain. Huffing, she crossed her arms and snapped out, "Rin! Stop it!"

Rin immediately stopped, eyes flickering over towards his sister for a moment before he scowled again. Kou just glared back at him, not amused in the least. This always happened whenever some guy came over to take her out. And while she may have stayed back and let Rin scare off those past guys, she wouldn't let Rin chase off her boyfriend.

So, intertwining their arms, Kou just looked at her brother with a warning look. "Rin, you are going to leave Seijuurou alone so that we can go along on our date. I won't let you chase off my boyfriend just because you have some crazy expectations for some guy to go out with me," Kou scolded before he turned to look at Seijuurou.

Attitude completely changing, Kou giggled again and moved a bit closer to Seijuurou. "Come on, Sei-kun, we should be going."

Unable to say anything, the swim captain just nodded his head before guiding Kou out of the house, closing the door behind him. Inside of the house, Rin just stared at the closed door for a moment, eyes a bit wide in shock. It didn't quite surprise him that Kou had acted like that. He did tend to run off her past boyfriends (and male friends) because he didn't like the sight of any of them around his little sister. Just the thought of their nasty, perverted hands on her...it made him want to strangle something.

Even someone as trustworthy as his swim captain was suspicious. There wasn't any reason to be, he knew that. The guy was practically a saint, if not a little bit excitable. The whole tough guy act that he usually put up during practice was just a front. He knew Seijuurou and knew his habits. He wasn't a womanizer like many liked to believe, nor was he completely obsessed with his swim club. He was a regular student who had fun, worked hard, and made sure that everyone under his watch was alright.

But the thought of him with his sister...it still made his stomach crawl.

So, Rin clutched onto his phone and quickly dialed the number that he had on speed-dial (not completely of free will). "...Hello? Nitori? ...Yeah, I need you to meet me outside of _Marco's_ in ten minutes. It's an emergency."

* * *

"S-Senpai? A-are...are you sure that this is a good idea?" Nitori asked softly as they crouched outside of the restaurant, hiding the behind the bushes.

Rin just scoffed and rolled his eyes, peaking over the bushes to try and catch a sight of his sister. However, from their position, he couldn't see any hint of them. He tried to spot them for a few more minutes before eventually giving up, sighing roughly. "There's got to be some way that we can see them...," he muttered to himself.

Seeing how upset Rin was becoming, Nitori nibbled his bottom lip and clutched onto his camera before hesitantly bringing a hand up and tapping the redhead on his shoulder. A flinch went through his body as Rin snapped his head towards him and he flushed. They stared at each other for a few moments before an expression of annoyance came across Rin's face.

"What?" he bit out, turning his attention back to the window.

Practically curling in on himself, Nitori thumbed the top of his camera. "W-well...maybe...maybe there's a way that we could get inside and spy on them there," he said softly, looking at Rin shyly.

Rin showed no signs that he was listening, but his ear twitched a little bit and his head tilted towards the grey-haired boy. "...What do you have in mind?"

* * *

_Ten Minutes Later_

"_Nitori,"_ Rin snarled out, glaring at the younger boy in irritation. "_Don't _tell me that you are actually serious about _this_." To prove his point, he waved his hand towards the people in question who were actually supposed to be helping him in the mess.

He didn't like this one bit.

Flushing, Nitori bowed his head for a moment before nodding it. "Y-yes, Senpai! Nagisa-kun suggested that we all pretend to be dating and get a bit table so that we can all watch over Gou-chan!"

Snarling even more, Rin let his eyes move over towards the other guys. Nagisa looked like the only one happy with the arrangement, jumping up and down in excitement. Everyone else, however, looked just as uncomfortable as he felt right now. Makoto was scratching the back of his head, standing behind Haruka with hesitant eyes. Haruka, on the other hand, was just standing there looking at Rin with a bored expression. The guy standing next to Nagisa seemed the most uncomfortable though, blushing and squirming around like he had something in his pants.

Grunting low in his throat, Rin glared at Nitori again. "And what makes you think that this will even work? It'll be impossible for all of us to blend in and act normal." Because honestly, Nitori just had to find the gang of misfits and ask them to help out.

This time, it wasn't Nitori who answered his concerns, but Nagisa instead. "Aww, come on Rin! There's no need to be worried! I'm sure that Gou-chan won't even see us~" Nagisa laughed loudly, drawing the attention of a few people who were walking past them.

Staring at Nagisa for a moment, Rin just sighed and pinched the bridge of his nose. There was no way that this was going to work.

* * *

Rin pulled at the clothing that Nagisa had forced him into, scowling even more. This was a terrible idea and he wouldn't be surprised in the least if they were turned down. Because honestly, they looked ridiculous.

However, none of it seemed to matter to Nagisa, who was dragging along that Rei guy right into the restaurant. Honestly, he wasn't sure how any of them dealt with the hyper blonde. He had barely been around his childhood friend and he was already tired. However, he had to bare with it, if he wanted to spy on his sister and his swim captain. So, stuffing his hands in his pockets, Rin followed everyone into the restaurant, ignoring all the stares that they were getting once they entered.

It was a pretty nice restaurant. It wasn't overly fancy, but it wasn't a diner or hangout spot by any means. Glancing around for a moment, Rin had to admit that he was mildly impressed by Mikoshiba's choice. _Mildly_ impressed.

"How may I help you gentlemen tonight?" the host at the front asked them in a "surprisingly" fake voice.

That just further fueled how much Rin thought they looked ridiculous.

Nagisa nodded his head quickly and glanced back at everyone before turning back towards the host. "Yeah! I have a table reserved for Hazuki. Table for six," he said almost seriously.

The host just lifted an eyebrow but glanced down at the piece of paper in front of him before nodding his head. He grabbed six menus and signaled them to follow behind him. Rin's own eyebrows flew up before they furrowed in confusion. How in the world...how had Nagisa been able to reserve a table for six of them so quickly? There was no way that the other boy could have known that they would call...

...Rin didn't really want to know. Something told him that he really didn't want to know.

As they were quickly seated and the orders for their drinks were taken, all six of them sat at the table, silently scouting the restaurant for signs of Kou and Seijuurou.

"Over there!" Nagisa hissed before hiding behind his menu, finger pointed to his right.

Everyone followed the direction that Nagisa was pointing and immediately tensed up as they saw the couple in question. Kou and Seijuurou were seated in one of the booths towards the back of the restaurant, already eating their food. And by the looks of things, they were really enjoying themselves.

Eyes narrowing, Rin lifted up his own menu and glared at the couple for a moment, hiding part of his face behind the piece of paper. He could see his swim captain holding his little sister's hand from across the table, his thumb rubbing the back of it almost subconsciously. There was a pleasant smile on both of their faces as they talked softly and ate. They looked so...so disgustingly couple-like.

It pissed Rin off.

"Stop scowling. You're drawing attention, Rin," Haruka said to him, kicking Rin under the table.

Cursing underneath his breath, Rin glared at Haruka, but calmed down his expression a bit. He could see out of the corner of his eyes that there were indeed other people in the restaurant _still_ looking at them. He really just wanted to turn around and demand what they were looking at, but that would quickly blow their cover. He couldn't do that, because they were far from done.

So, turning his attention to the menu, Rin stilled for a moment and looked up at Nagisa. "...Hey, who's paying for this meal, by the way?" he asked.

Everyone stopped what they were doing and stared at Rin like he was crazy. He didn't like those looks. Snarling, he put down his menu and looked at each one of them. "What are you staring at? I'm completely serious. Who's paying for this meal?"

A sheepish expression came to Makoto's face. "We thought you were," he admitted softly.

"What?! Why?" he asked incredulously. What in the world?! Why would they think something like that? It wasn't even his idea to come into the restaurant like this in the first place!

"W-well...Nitori-kun said that you would help pay for anything as long as you could check in on your sister-"

"_NITORI-" _Rin snarled out, right above a whisper. He moved to grab the grey-haired boy, who just squeaked and moved away from him as quickly as he could.

However, he wasn't quick enough and Rin quickly pulled him into a headlock, growling low in his throat. "I should beat the crap out of you, you know that Nitori?" he hissed out, eyes gleaming dangerously.

"B-But R-Rin-sempai, y-you can't!" Nitori squeaked out, tears prickling out of the edges of his eyes.

"And why not?" Rin's grip grew tighter around Nitori's neck and he could see the other boy's face growing red.

"Because w-w-we're in a restaurant," he panted out, breathing growing heavy.

At that, Rin froze for a moment, staring down at Nitori for a moment. He blinked his eyes before scoffing and releasing the boy, moving back to his seat and brushing off his clothing. Oh, he would be getting back the brat when they got out of the restaurant, that was assured. Sighing roughly, Rin picked the menu back up and scanned the prices of the food items, cringing as he saw the steep prices.

Glaring at everyone, Rin narrowed his eyes dangerously. "If any of you even think about buying that lobster or Filet mignon, I will personally skin you alive and throw your remains in the ocean," he hissed out.

And with that, the tension around the table increased tenfold.

* * *

Eyes flickering towards the table just a few feet away from their's, Kou rolled her eyes and tightened her grip around Seijuurou's hand. "Do they really think that we can't see them? Let alone hear them?" she asked with a laugh.

Why in the world they thought that they could hide themselves when they stayed together, she had no clue. But somehow, she couldn't find it in herself to really be mad. She should be, by all means. Her brother went behind her back and decided to spy on her when she had specifically told him that she didn't need a babysitter for her date. Any other sister would have been furious.

But Kou, she wasn't furious. She wasn't even annoyed. No, she was more amused if anything. Not to mention a little bit interested.

Looking at the table of swimmers, she hummed curiously and narrowed her eyes a little bit. She noticed the close proximity that Makoto and Haruka had, not that she was really surprised. The two males were always really close, even during swimming practices lately. They were like an old married couple. So, when she saw Makoto's hand slid off of the table and a faint blush come to Haruka's face before he smiled slightly, she giggled and took a bite of her steak. They were really cute together.

The two that did catch her off guard though, were Rei and Nagisa. Not because she hadn't known that there was chemistry there, because there was. The sexual tension between them alone was enough to fuel an entire city. She was more surprised by the fact that they were actually getting their heads out of their butts, apparently. They actually looked like a cute date, if it weren't for the other occupants of the table.

And speaking of the other occupants...

"Is it just me, or does Rin look like he's about to maul that poor kid?" Kou asked in slight worry, looking at Seijuurou.

The swim captain pulled away from his food for a moment, eyes wide and blinking before he turned his head to where everyone was sitting. He then laughed and shook his head, waving a hand in the air. "Ah, don't worry about Nitori. Rin wouldn't harm a hair on his head."

Kou just raised an eyebrow in skeptism before shrugging and returning to her food. While she wanted to disagree with that, what with the way that Rin was holding onto the boy's wrist, she found that it wasn't really her problem.

After all, Rin was the one who decided that spying on her during her date was a good idea.

* * *

Noticing movement out of the corner of his eyes, Rin peeked over towards the table where his sister was sitting and cursed. They were already paying for their bill and standing up to leave. Hissing at the others for a moment, everyone stopped what they were doing and looked at Rin with ranging expressions on their face. He tilted his head towards his sister and Seijuurou, who were walking down one of the many aisles to get out.

All of their eyes widened and they slid down in their chairs to avoid being seen. However, many of them (mainly Makoto, Rei, and Rin) were too broad and tall to hide. So, when Kou and Seijuurou stopped at their table, all of them couldn't help but look sheepish and embarrassed.

Kou crossed her arms and huffed at all of them. "I should be mad at all of you. This was supposed to be a date between me and Sei-kun, not us and you guys."

A faint blush came to all of their cheeks and they bowed their heads in shame. However, some of the tension left their bodies when they heard Kou giggling softly. Lifting his head up, Rin raised his eyebrows in question. "What's so funny?" he asked gruffly, lifting himself out of the seat and sitting up straight.

"What's so funny is the fact that you guys are basically having a triple date while spying on my and Seijuurou, and you don't even realize it, brother. Have fun~" Kou said happily before taking her boyfriend's hand and leading him out of the restaurant.

Rin stared at his sister's retreating form for a moment before flushing and standing up in indignation, pointing at Kou. "T-This is not a date!"

* * *

**A/N: ...Yeah, that's about it. This is based off of a prompt I remember seeing around tumblr somewhere. Oh, and I still abuse time breaks because it makes things much more funny. **


End file.
